Method for manufacturing optical access units, an optical access unit and an optical fiber ferrule module

ABSTRACT

A method and an optical fiber access unit in which a fiber is optically connected to a transmitter and/or receiver chip. Said chip is in turn connected to an electronic circuit for signal processing and said circuit is connected to a coupling port for distributing signals to and from said circuit and fiber. A fiber ferrule module is formed by an optical fiber and a casing surrounding the fiber except for its two ends that are prepared to form optical interfaces. A transmitter/receiver chip module is arranged for optical connection to a first access end of the fiber ferrule module and a fiber access port is provided for optical connection at a second access end of the fiber ferrule module. A support unit is finally arranged for assembling the fiber ferrule module, the transmitter/receiver chip module and the electronic circuit.

TECHNICAL FIELD

[0001] The invention relates to a method for manufacturing optical fiberaccess units and such a fiber access unit wherein a fiber is opticallyconnected to a transmitter/receiver chip, said chip being connected toan electronic circuit for signal processing and said circuit beingconnected to a coupling port for distributing signals to and from saidcircuit and fiber. The invention further relates to an optical fiberferrule module for use in such a fiber access unit.

BACKGROUND OF THE INVENTION

[0002] Network communications including domestic access networks aremore and more based on optical fibers. When integrating optical fibersand electronics there is a need for an optical interface including afiber coupling device of some standard design and an electronic circuitfor transmitting electrical signals into optical signals and vice versa.The coupling device and the electronic circuit are connected to eachother by a short optical fiber of a standard multimode or singlemodetype. Normally the fiber coupling device, the short fiber connection andat least the transmitter/receiver chip of the electronic circuit areassembled to a sub-module, which in turn is to be installed in the totalinterface unit. The sub-module has to be treated with great care bothwhen assembled and handled because of its sensitive connections at thetwo fiber ends. The fiber coupling end has to be very well polished andthe chip end stripped and accurately cut and in particular the later ishard to achieve and the module is easily broken or damaged when handledin the next mounting step.

SUMMARY OF THE INVENTION

[0003] The known manufacturing principle is not well adapted tolarge-scale production mainly because of low productivity and highcosts. Many operations have do be performed by hand and are not possibleto transfer into an automatic production line. Another problem is thatknown methods do not give reliable and even quality on the producedsub-modules and many of them have to be rejected and scrapped.

[0004] For that reason, one object of the present invention is toachieve a method, a fiber access unit and a fiber ferrule module thatgive the possibility of large scale industrial production of fiberaccess units for connection to microelectronic devices. Another objectis to provide a method and an arrangement that give the possibility tomove the components and modules in an automatic line without humanassistance. Yet another object is to accomplish a fiber ferrule modulethat is easy to manufacture and handle as one separate unit. Stillanother object is to achieve a method that ensures an even quality ofthe manufactured fiber access unit.

[0005] Briefly, these objects of the present invention are accomplishedby a method and an optical fiber access unit in which a fiber isoptically connected to a transmitter and/or receiver chip. Said chip isin turn connected to an electronic circuit for signal processing andsaid circuit unit is connected to a coupling port for distributingsignals to and from said circuit and fiber. A fiber ferrule module isformed by an optical fiber and a casing surrounding the fiber except forits two ends that are prepared to form optical interfaces. Atransmitter/receiver chip module is arranged for optical connection to afirst access end of the fiber ferrule module and a fiber access port isprovided for optical connection at the second access end of the fiberferrule module. A support unit is finally arranged for assembling thefiber ferrule module, the transmitter/receiver chip module and theelectronic circuit.

[0006] An advantage of the present invention is that it enables allparts in a fiber access unit to be treated as modules in an automaticproduction line. Another advantage is that the sensitive fiber is fullycovered and protected against damages during the whole period from themanufacturing of the ferrule module to the assembling of the fiberaccess unit. A further advantage is the possibility to integrate thetransmitter/receiver chip with the ferrule module to one unit. Yetanother advantage is that the two ends of the fiber in the ferrulemodule can be polished in one and the same process when secured in theferrule casing. Still another advantage is that the access ports of thefiber access unit can easily be adapted to different standardconnections.

[0007] Other objects, advantages and novel features of the inventionwill become apparent from the following detailed description whenconsidered in conjunction with the accompanying drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The invention will be described more in detail with reference tothe following drawings, in which:

[0009]FIG. 1 shows schematically a perspective overview of an opticalfiber ferrule module according to the invention,

[0010]FIG. 2 shows schematically a perspective view of an alternativeoptical fiber ferrule module according to the invention,

[0011]FIG. 3 shows schematically a perspective view from the oppositeside of an optical fiber ferrule module according to FIG. 2,

[0012]FIG. 4 shows schematically a perspective view of a partlyassembled optical access unit including a single fiber ferrule moduleaccording to FIG. 1,

[0013]FIG. 5 shows schematically a perspective view of a partlyassembled optical access unit including two single fiber ferrule modulesaccording to FIG. 1,

[0014]FIG. 6 shows schematically a perspective view of a partlyassembled optical access unit including a ferrule module according toFIG. 2,

[0015]FIG. 7 shows schematically a perspective view of an optical accessunit including a single fiber ferrule module according to FIG. 1,

[0016]FIG. 8 shows schematically a perspective view of an optical accessunit including two single fiber ferrule modules according to FIG. 1 and

[0017]FIG. 9 shows schematically a perspective view of an optical accessunit including a ferrule module according to FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

[0018] In FIG. 1, there is shown an optical fiber ferrule module 11,comprising a central optical fiber 12 or fiber unit with a first 13 anda second end 14 and a cylindrical casing 15 surrounding the fiber 11except for its two ends. The fiber is a standard optical fiber,preferable of singlemode type and the casing of some solid materialnormally used for optical ferrules, e.g. ceramic material of zirconium,glass or polymers. The casing 15 comprises a first 16 and a second 17end face that are in flush with the first 13 and second 14 end of thefiber 12. The end faces are substantially planar and perpendicular tothe longitudinal direction of the fiber. In practice that means that theend faces are somewhat dome-shaped with a radius of 10-25 mm with thefiber ends located in the middle in order to obtain close contact withconnecting fiber or electronics. The first end face 16 with its fiberend 13 compose a first access end 18 adapted for said electronicsconnection and the second end face 17 with its fiber end 14 compose asecond access end 19 adapted for said external fiber connection. Thecasing 15 is provided with a ring-shaped groove 20 or grooves on thesurface in order to facilitate mounting.

[0019] The ferrule module 11 is one module in a fiber access unit 21according to FIG. 7. Other parts appear from FIG. 4, that shows asupport base plate 22 on which the ferrule module 11 and necessaryelectronics are mounted. The first access end 18 with its first fiberend 13 is in a usual manner arranged with a small gap very close to atransmitter in the form of a laser chip or a receiver in the form of adiode chip. They could also as usual be combined to a transceiver chip.In the present text the phrase transceiver/receiver chip will be used tocover all alternatives. In FIG. 4, a standard transmitter/receiver chip23 is arranged on a chip module 24. The chip module 24 is in turn bondedto the necessary electronic circuits 25 for driving thetransceiver/receiver module 24 and distributing signals to and from theaccess unit 21. Electric distribution of signals to and from the accessunit is accomplished by a coupling port 26 in the form of a number ofleads 27 bonded to the electronic circuits 25. Optic fiber distributionof signals to and from the access unit is in turn accomplished by afiber access port 28 in the form of a protruding part 29 of the ferrulemodule 11.

[0020] The base plate 22 and a cover plate 30 compose a support unit forthe ferrule module 11 and the electronic circuits 25. The base plate 22and the cover plate 30 are formed to receive the ferrule module 11 in asocket 31 comprising a track means 32 corresponding to the groove in thecasing 15.

[0021] In FIGS. 5 and 8, there is shown a second embodiment of a fiberaccess unit according to the invention, in which two ferrule modules 11′and 11″ with transmitter/receiver chip modules 24′ and 24″ are arrangedon the same support unit 22, 30. This enables simultaneous transmittingand/or receiving and double signaling capacity.

[0022] The ferrule module can have many different shapes and include avaries number of fiber units. In FIGS. 2 and 3, there is shown a ferrulemodule 41 of a box-like configuration with four fiber units 42, havingfirst 43 and second 44 ends in flush with a first 46 and a second 47 endface of the box-like casing 45. The first end face 46 is arranged toreceive a transmitter/receiver chip module 51 in a recess 52 in thecasing 45. The recess 52 and the module 51 are carefully fit to eachother by guiding means in the form of tracks 53. The number oftransmitter/receiver chips 50 corresponds to the number of fiber units42. There are two holes 54 in each end face 46, 47 to enable insertionof not shown guiding pins. The second end face 47 with the second fiberends 44 compose a fiber access port 48 for connection with externalfibers. The casing 45 also comprise a flange or groove 49 to facilitatemounting and guiding in the support unit. For other parts in FIGS. 6 and9, the same reference numbers are used as for the similar parts in thefirst embodiment.

[0023] The manufacturing of fiber access units according to theinvention could in a preferred example start with forming a ferrulemodule in a typical ferrule forming process. One normal process is tocast a ceramic material to the shape of the casing 15; 45 leaving thinholes for the fibers 12; 42. The fibers are then fixed in the holes bygluing with a suitable resin and after setting, the end faces 16, 17;46, 47 with the exposed fiber ends 13, 14; 43, 44 are polished in oneprocess to achieve good light transmitting properties. The ferrule unitsare then handled and stored as one module in the subsequent assemblingsteps of the fiber access units 21. The transmitter/receiver chip unitis also assembled and handled as one chip module 24; 51 that is easy tomount on the ferrule module, as in FIG. 3, or directly on the base plate22, as in FIGS. 4 and 5. The next step is known as such and includes thearrangement of necessary electronic circuits 25 on the base plate 22,bonding to the leads 27 etc. Finally the cover plate 30 is mounted onthe base plate to cover all electronic circuits and lock all detailsincluding the coupling port 26 for the electric signaling and the fiberaccess port 28; 48 for the optic signaling.

[0024] The invention can be put into practice in many other ways. Theconfiguration and material of the ferrule module can be varied as wellas the arrangement of the electronic circuits in the support unit. Theaccess ports can also be adapted to different standards andapplications.

1. A method for manufacturing optical fiber access units wherein a fiberis optically connected to a transmitter/receiver chip, said chip beingconnected to an electronic circuit for signal processing and saidcircuit being connected to a coupling port for distributing signals toand from said circuit and fiber comprising the steps of: forming anoptical fiber ferrule module comprising a casing and two access ends, afirst one adapted for transmitter/receiver chip connection and a secondone adapted for fiber connection, forming a transmitter/receiver chipmodule for connection to the first access end of the fiber ferrulemodule, providing a support unit for the fiber ferrule module, thetransmitter/receiver chip module and the electronic circuit, assemblingthe modules and the electronic circuit, connecting the coupling port tothe electronic circuit and providing a fiber access port at the secondaccess end of the fiber ferrule module.
 2. The method according to claim1, wherein that the step of forming the fiber ferrule module comprisesthe steps of: providing a solid casing around the fiber with end facesin line with the fiber ends and polishing the fiber ends by grinding theend faces.
 3. The method according to claim 2, further comprising thesteps of: arranging a through hole in the casing for the fiber and,fixing the fiber in the hole by gluing.
 4. An optical fiber access unitcomprising: a fiber unit which is optically connected to atransmitter/receiver chip; said chip being connected to an electroniccircuit for signal processing; said circuit being connected to acoupling port for distributing signals to and from said circuit andfiber; a fiber ferrule module (11; 41) is adapted for fiber connectionand transmitter/receiver chip connection, wherein the fiber ferrulemodule further comprises the fiber unit, a casing and two access ends tothe fiber unit, a first one adapted for transmitter/receiver chipconnection and a second one adapted for fiber connection, wherein saidtransmitter/receiver chip module is arranged for connection to the firstaccess end of the fiber ferrule module, a support unit is arranged forassembling the fiber ferrule module, the transmitter/receiver chipmodule and the electronic circuit and a fiber access port is provided atthe second access end of the fiber ferrule module.
 5. An optical fiberaccess unit according to claim 4 wherein that the casing is made ofsolid material surrounding the fiber and comprises end faces in linewith the fiber ends and the access ports comprise said end faces.
 6. Anoptical fiber access unit according to claim 4 wherein that the fiberferrule module comprises two or more fibers and the transmitter/receiverchip module comprises a chip for each one of the fibers.
 7. An opticalfiber access unit according to claim 5 wherein that guiding means arearranged for aligning the ferrule and chip modules.
 8. An optical fiberaccess unit according to claim 5, wherein that the end faces are planarand substantially perpendicular to the longitudinal direction of thefiber.
 9. A fiber ferrule module for use in an optical fiber accessunit, said module comprising: a fiber with a first and a second endforming optical interfaces; wherein the fiber is surrounded by a casingover its whole length between its two ends, the casing further comprisesend faces in flush with the first and the second end of the fiber, thefirst end of the fiber is arranged for optical connection to antransmitter/receiver chip and the second end of the fiber is arrangedfor optical connection to an external fiber.
 10. A fiber ferrule moduleaccording to claim 9, that: the fiber is a single mode fiber.
 11. Afiber ferrule module according to claim 9 wherein that: the casing ismade of a material with ceramic properties and comprises a ring shapedgroove or flange on its surface for engagement with a surroundingsupport.
 12. A fiber ferrule module according to claim 9, wherein that:two or more fibers are located in the casing.